Anyone have a reliable printable chart or calculator for panel CTE and clip spacing on long runs, plus a galvanic compatibility matrix for fasteners and trim? I’m updating our seacoast spec (2 miles inland, Zone 2A) to favor PVDF Galvalume and 0.040 aluminum with 316 SS fasteners, and I want a reference that ties thermal movement to panel length and backs up the corrosion resistance choices.
For your ‘2 miles inland’ Zone 2A spec, I use Sheffield Metals’ thermal movement calculator (https://sheffieldmetals.com/resources/metal-roof-thermal-movement-calculator/) at a 75–100°F swing and upsize floating-clip slots/end clearances so a 60’ PVDF Galvalume run allows about 3/8 in total travel; print that with the MCA galvanic chart and you’ve got both CTE and compatibility covered — just isolate 316 SS from 0.040 aluminum at wet laps with butyl and coated washers. What’s your longest panel run?
Print the galvanic matrix here: https://www.fastenal.com/content/feds/pdf/Article%20-%20Galvanic%20Corrosion.pdf; for expansion vs run length, lean on the profile-specific clip tables from MBCI or ATAS so your PVDF Galvalume and 0.040 aluminum spec matches the actual clip/pad. Small caveat: 316 SS on aluminum needs isolators under the head and at trim laps, and keep copper out of that stack in Zone 2A. I can share a one-pager I use that ties delta-T to run length and clip count.
I keep MCA’s thermal movement table and their galvanic matrix printed: MCA Metal University - Technical Resources, White Papers, Continuing Ed for Metal Building Materials; for ‘PVDF Galvalume’, add nylon isolators under trims — ok?
I use the NRCA Roofing Manual (Metal Panel) tables for coefficients and clip movement allowances, then cite MIL-STD-889 for the galvanic pairing; here’s a clean public copy: ASSIST-QuickSearch Document Details. Small caveat: set your delta T from local ASHRAE highs/lows instead of a generic 75°F, and add nylon isolators under trim where dissimilar contacts are unavoidable — want a one-page cheat sheet I give to crews?
Skip the generic charts and write the calc into the spec: ΔL = α·L·ΔT; on a 60’ run and 100°F swing you’re at about 0.47" for coated steel and about 0.94" for 0.040 aluminum, so size clip travel/spacing to that. For metals pairing, I add AGA’s dissimilar-metals chart to the submittal: https://galvanizeit.org/design-and-fabrication/design-considerations/dissimilar-metals, plus isolators anywhere aluminum touches steel near the coast. @evan_blake’s MIL-STD note is good, but avoid hard 410 screws anywhere near salt — curious what ΔT you’re assuming at 2 miles.
, hunting for clean charts is a pain — quick win: print Sheffield Metals’ “Galvanic Action” and “Thermal Movement” tech bulletins; they cover 316 with PVDF Galvalume and 0.040 aluminum and give cite-able CTEs: The Metal Roofing Learning Center® - Sheffield Metals. Small caveat for your 2-mile-inland 2A spec: call out dielectric shims under SS clips on aluminum pans and minimum clip slot travel sized to your worst seasonal swing; do you want a single-page handout or an editable calc appendix?
I set ΔT via climate.onebuilding.org for “2 miles inland”; cite SMACNA’s galvanic chart. Confirm your panel’s clip travel.